Phonograph



Jan. 2, 1940. A, V BEDFORD 8 2,185,882

PHONOGRAPH Filed Aug. 29, 1936 2 Sheets-Sheet l Jay. 2, 1940. A. v:BEDFQRD 2,185,882

PHONOGRAPH Filed Aug. 29, 1936 2 Sheets-Sheet 2 Patented Jan. 2, 1940PHONOGRAPH Alda V. Bedford, Collingswood, N. J., assignor to RadioCorporation of America, a corporation of Delaware Application August 29,1936, Serial No. 98,445

15 Claims.

This invention relates to record moving mechanisms, and moreparticularly to a method of and means for controlling the speed ofrotation of a phonograph turntable or equivalent sound record supportingdevice.

In conventional phonographs, the turntable is usually driven by asuitable motor through reduction gearing or the like. Despite the careexercised in gear manufacture, slight mechanical imperfections existtherein, and these imperfections or inaccuracies produce irregularitiesin the rotational speed of the turntable which are deleterious to highquality reproduction of sound. In designing turntables, especially thosefor operation at low speeds (for example, 33 R. P. M.), it has beenproposed to use flexible couplings between the driving motor and theturntable and massive rotating fly-wheels on the turntable in order tofilter out irregularities caused by nonuniform pitch in gears of thespeed reducing systems. While such filters may be satisfactory forirregularities of relatively high frequency, they are entirely unsuitedto filter out irregularities which are of repetition frequencies of oneor two times the turntable rotation frequency on account of the extrememassiveness required of the aforementioned fly-wheels for such lowfrequencies.

The primary object of my present invention is to provide an improvedmethod of and means for controlling the rotational speed of phonographturntables, or any other apparatus including a rotating member intendedto be rotated at uniform speed, whereby the foregoing difiiculty isobviated.

More specifically, it is an object of my present invention to provide,in phonographs, novel means for counteracting the effect of variouselements which tend to produce irregularities in the speed of theturntable where the irregularities have a whole number frequencyrelation to the turntable rotation frequency.

A further object of my present invention is to provide improved speedcontrolling means as aforesaid which is relatively simple inconstruction. which may be applied to existing phonoraphs withoutmaterial alteration thereof, and which is highly effective in use.

In accordance with my present invention, I provide means fordeliberately introduc ng additional uniformly-variable torque in therotating system. One component of the added torque is made to varyuniformly at turntable rotation frequency and is adjustable both inphase and amplitude. The adjustment may be made while the turn- (Cl. M-604) table is rotating and preferably with test conditions under whicha continuous indicating means is employed to indicate when the optimumadjustment is reached. If desired, the adjustment I may be made whilelistening to the reproduc- 6 tion of a recorded steady tone instead ofby the use of the indicating means. Either the same means which providesthe aforesaid torque component or similar other means may be employed tosupply additional torque of higher frequencies of variation, such as thesecond or third multiples or harmonics of-the turntable rotationalfrequency. The added torques of each frequency may be adjusted, one at atime, to buck out the corresponding effect caused by imperfections ofthe driving system.

The novel features that I consider characteristic of my invention areset forth with particularity in the appended claims. The inventionitself, however, both as to its organization and method of operation,together with additional objects and advantages thereof, will best beunderstood from the following description of several embodiments thereofwhen read in connection with the accompanying drawings in which Figure 1is a side elevation of one form of my present invention,

Figure 2 is a partial plan and partial sectional view taken on the line2-2 of Fig. 1, 30

Figure 3 is a similar view taken on the line 33 of Fig. 1,

Figure 4 is a similar view taken on the line 44 of Fig. 1,

Figure 5 is a similar view of a modified form of my invention, and

Figure 6 is an elevational view of the structure shown in Fig. 5.

Referring more specifically to the drawings, wherein similar referencecharacters indicate corresponding parts throughout, there is shown, inFig. 1, a turntable I supported on a bearing 3 and driven by a shaftcomprising-the shaft sections 5a, 5b and 5c. The shaft section 5arotates in the bearing 3 and is coupled to the shaft section 522 bymeans of a flexible coupling 1 of any suitable type. The shaft section5b is similarly coupled to the shaft coupling by a flexible coupling 9,the section 5b rotating in bearings II and I2 and having fixed thereon aflywheel l3, while the shaft section 50 rotates in bearings 15 and I7and has a worm wheel 19 fixed thereto which meshes with a worm 2| on theshaft 23 of a driving motor (not shown). Also fixed to the shaft section5b are a plurality changes therein are possible.

which has a plurality of rollers 3| engaging its cam surface orperiphery. The rollers 3| are carried by resilient strips 33, such asspring blades, which are mounted on blocks 35 of a stationary frame andmay be adjustably pressed against the cam edges of their respectivelyassociated cams by an adjusting screw 31 threaded into an extension 39on each of the blocks.

The cam 25 is so shaped that each roller 3| produces on the shaft atorque which varies according to a sine wave around the periphery of thecam. A circular disk eccentrically mounted on the shaft section 5b willsuflice forv this purpose. The cams 21 and 29 are so shaped,respectively, as to produce two and three sine wave cycles of torque foreach revolution thereof, or for each turn of the shaft section 5b. Anynumber of rollers may be employed in association with each cam. I haveshown four rollers in association with the cams 25 and 29 (Figs. 2 andspaced physically from each other about the peripheries of the cams andeffectively operated 90 apart with respect to one cycle of the torquewave produced thereby so that, by proper adjustment of the screws 31,the total torque supplied by either cam can be adjusted in amplitude andin phase over 360. The four rollers associated with the cam 21 (Fig. 3),on the other hand, are physically spaced equally over approximately ofthe whole cam surface, but the same 90 spacing or effect with respect tothe sine wave is produced by this arrangement since the four rollersare, in this case, also distributed over a single cycle of the torquewave. In the arrangements shown in Figs. 2 and 4, the rollers are spacedover 360' of the cam surface merely for the sake of convenience from amechanical standpoint.

The purpose of the flexible coupling 9 is to permit the speed of thefiy-wheel I3 to be made substantially steady by the torque provided bythe several cams 25, 21 and 29 without having to alter the speed of themotor in the event that the worm wheel or gear l9 has non-uniform toothpitch, as is usually the case. The inertia of the turntable l and theflexibility of the coupling 1 will act to reduce high frequencyvariations in the turntable speed.

In Figs. 5 and 6, I have shown a modification of my invention whereinonly two rollers 3| are employed in association with the cam 25. In thismodification, the springs 33 which carry the rollers 3| are secured toopposite ends of an arm 4| which is rotatably carried on the shaftsection 5b midway between the ends of the arm. A

threaded extension 43 on one end of the arm 4| extends through a slot 45in an arcuate guide member 41 which is concentric with the shaft section51), a wing nut 49 being received by the extension 43 for clamping thearm 4! in any desired position along the guide member 41. By merelyloosening the wing nut 49 and rotating the arm 4| on the shaft 5b, therollers 3| may be adjusted circumferentially on the cam 25 to providephase adjustment of the added torque. The same result may be effected,if desired, by arranging the arm, 4| in a fixed position and mountingthe cam 25 on the shaft 517 for circumferential adjustment upon theshaft.

Although I have shown and described several embodiments of my invention,I am fully aware that many other modifications thereof and For example,the cams 25, 21 and 29 may each be placed in differof axially spacedcams 25, 21 and 29, each of ent locations in the drive system withrespect to v the filtering and driving elements or-parts of the filter.Also, the flexible coupling 9 may be omitted, if desired, in which case,the motor would be required to vary its speed in response to thevariable torques produced by the several cams. Furthermore, each of thecams may be made to alter the torque by supplying a variable brakingeffect, as by substituting brake pads for the rollers 3|. It is alsopossible to obtain a different type of correction by arranging the cams25, 21 and 29 in such a manner that they will add a definite additionalvariable rotation to the system, as, for example, by superimposingoscillatory motion of the worm 2| along its axis. Other modificationsand changes will be apparent to those skilled in the art. I thereforedesire that my invention shall not be limited except insofar as isnecessitated by the prior art and by the spirit of the appended claims.

I claim as my invention:

In a phonograph, the combination of a driving shaft, a turntablearranged to be driven thereby, a cam fixed to said shaft for rotationtherewith, means pressingly applied-to the cam surface of said cam forapplying a variable torque to said shaft as it rotates, and means foradjusting said first named means circumferentially with respect to saidcam surface.

2. In a phonograph, the combination of a driving shaft, a turntablearranged to be driven thereby, a cam fixed to said shaft for rotationtherewith, means pressingly applied to the cam surface of said cam forapplying a variable torque to said shaft'as it rotates, means foradjusting the pressure between said first named means and said cam, andmeans for adjusting said first named means circumferentially withrespect to said cam surface.

3. In a phonograph, the combination of a driving shaft, a turntablearranged to be driven thereby, a cam fixed to said shaft for rotationtherewith, means pressingly applied to the cam surface of said cam forapplying a variable torque to said shaft as it rotates, said cam beingso shaped that the torque produced on said shaft varies according to asine wave around the cam surface thereof, and means for adjusting saidfirst-named means circumferentially with respect to said cam surface.

4. In a phonograph, the combination of a driving shaft, a turntablearranged to be driven thereby, a cam fixed to said shaft for rotationtherewith, means pressingly applied to the cam surface of said cam forapplying a variable torque to said shaft as it rotates, said cam beingso shaped that a small whole number of sine wave cycles of torque areapplied to said shaft for each revolution of said shaft, and means foradjusting said first-named means circumferentially with respect to saidcam surface.

5. In a phonograph, the combination of a driving shaft, a memberarranged to be driven by said shaft and adapted to support a record,means for applying to said shaft a sine wave torque, and additionalmeans for applying to said shaft at least one other sine wave torquedifiering in phase by 90 from said first-named torque.

6. In a phonograph, the combination of a driving shaft, a memberarranged to be driven by said shaft and adapted to support a record,means for applying to said shaft a. uniformly variable sine wave torqueone component of which varies uniformly at the rotation frequency ofsaid member, and additional means for also greases applying to saidshaft a uniformly variable torque which is a whole multiple or harmonicof the rotation frequency of said member.

'7. In a phonograph, the combination of a driving shaft, a turntablearranged to be driven thereby and rotatable in response thereto, aplurality of cams flxed to and rotatable with said shaft, and meansassociated with each of said cams for applying a variable torque to saidshaft, at least one of said cams being so constructed and arranged as toproduce a sine wave torque which varies uniformly at the rotationfrequency of said turntable, andat least one other of said cams being soconstructed and arranged as to produce a sine wave torque which variesuniformly, at a frequency which is a whole multiple or harmonic of theturntable rotation frequency.

8. The invention set forth in claim 7 characterized by the addition ofmeans for varying at least one of said torques in both phase andamplitude.

9. In a phonograph, the combination of a driving motor, a shaft driventhereby, said shaft including a plurality of sections, a flexiblecoupling between two of said sections; said motorbeing coupled to one ofsaid two sections, a plurality of cams fixed to the other of said twosections and rotatable therewith, and means associated with each of saidcams for applying a variable torque to said shaft.

' 10. In a phonograph, the combination of a rotatable input, memberhaving periodic variations in speed, an output member, flexible meanscoupling said output member to said input member, and means for applyingperiodic variations of torque to said output member whereby said outputmember is caused to oscillate with respect to said input member at thefrequency of said periodic variations .to effect uniform rotation ofsaid output member while permitting said input member to rotate withsaid periodic variations.

11. In phonographic apparatus having an output member intended to berotated at a steady speed, the combination with said output member of arotatable input member having a substantially uniform average speed andsubject to undesired periodic speed variations recurring at thefrequency of rotation of said input member such that said input memberperiodically runs first ahead and then behind its average angularposition, flexible means coupling said input member to said outputmember, a stationary frame, and means for applying additional variabletorque between said stationary frame and said output member inaccordance with the instantaneous angular position of said output memberrelative to said frame input member and substantially independently ofthe speed and inertia of said output member whereby said output memberis acterized by the addition of means for adjust-' lng said additionaltorque applying means in angular phase and in amplitude.

14. The invention set forth in claim 11 characterized in that saidoutput member is provided with at least one cam and characterizedfurther in that said variable torque applying means is constituted by aspring actuated follower in engagement with said cam.

15. The invention set forth in claim 11 characterized in that saidoutput member is provided with at least one cam, characterized furtherin that said variabletorque applying means is constituted by a springfollower in engagement with said cam, and characterized still further bythe addition of means for adjusting said spring follower angularly aboutsaid cam whereby to vary the angular phase of said additional torque.

' ALDA V. BEDFORD.

